What is a Enocder sensor ?

[Dave Scheck]

Originally Posted by EricH

an encoder, as far as I know, counts how many times its own shaft rotates (oh wait, that's a potentiometer...or is it?)

Encoders and potentiometers can come in similar form factors, but their internals are quite different.

In general, potentiometers output a DC signal that is proportional to the absolute position of the internal wiper connected to its shaft. If you apply a 5 Volt differential to the outer pins of the pot, the wiper pin will have an analog range of 0-5Volts. Pots are a good match for your application if you have a fixed range of motion.

As for encoders, they are used to measure relative position. They output a pulse as the shaft rotates. It is up to whatever is connected to the encoder to count these pulses and make sense of the data.

On a very basic level, think of the spokes on a bicycle wheel. Imagine holding a straw between the spokes and rotating the wheel. You can determine how many rotations that wheel has made by counting the number of times the straw hits a spoke.

In reality, there are components within the encoder housing that detect the rotation of the shaft. You only need to be concerned with counting the pulses.

Encoders are a good match for your application if there are no fixed ends to your range of motion, such as wheel rotations. You can also use it for something like our (111) lift last year, however, you will probably need to incorporate some sort of home-switch to know your absolute position (since the encoder only gives you relative position).